/*
 * CharacterArrayTransform.java May 2007
 *
 * Copyright (C) 2007, Niall Gallagher <niallg@users.sf.net>
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or
 * implied. See the License for the specific language governing
 * permissions and limitations under the License.
 */

package wx.xml.simpleframework.xml.transform;

import java.lang.reflect.Array;

/**
 * The <code>CharacterArrayTransform</code> is used to transform text
 * values to and from string representations, which will be inserted
 * in the generated XML document as the value place holder. The
 * value must be readable and writable in the same format. Fields
 * and methods annotated with the XML attribute annotation will use
 * this to persist and retrieve the value to and from the XML source.
 * <pre>
 *
 *    &#64;Attribute
 *    private char[] text;
 *
 * </pre>
 * As well as the XML attribute values using transforms, fields and
 * methods annotated with the XML element annotation will use this.
 * Aside from the obvious difference, the element annotation has an
 * advantage over the attribute annotation in that it can maintain
 * any references using the <code>CycleStrategy</code> object.
 *
 * @author Niall Gallagher
 */
class CharacterArrayTransform implements Transform {

    /**
     * This is the entry type for the primitive array to be created.
     */
    private final Class entry;

    /**
     * Constructor for the <code>PrimitiveArrayTransform</code> object.
     * This is used to create a transform that will create primitive
     * arrays and populate the values of the array with values from a
     * comma separated list of individual values for the entry type.
     *
     * @param entry this is the entry component type for the array
     */
    public CharacterArrayTransform(Class entry) {
        this.entry = entry;
    }

    /**
     * This method is used to convert the string value given to an
     * appropriate representation. This is used when an object is
     * being deserialized from the XML document and the value for
     * the string representation is required.
     *
     * @param value this is the string representation of the value
     * @return this returns an appropriate instanced to be used
     */
    public Object read(String value) throws Exception {
        char[] list   = value.toCharArray();
        int    length = list.length;

        if (entry == char.class) {
            return list;
        }
        return read(list, length);
    }

    /**
     * This method is used to convert the string value given to an
     * appropriate representation. This is used when an object is
     * being deserialized from the XML document and the value for
     * the string representation is required.
     *
     * @param list   this is the string representation of the value
     * @param length this is the number of string values to use
     * @return this returns an appropriate instanced to be used
     */
    private Object read(char[] list, int length) throws Exception {
        Object array = Array.newInstance(entry, length);

        for (int i = 0; i < length; i++) {
            Array.set(array, i, list[i]);
        }
        return array;
    }

    /**
     * This method is used to convert the provided value into an XML
     * usable format. This is used in the serialization process when
     * there is a need to convert a field value in to a string so
     * that that value can be written as a valid XML entity.
     *
     * @param value this is the value to be converted to a string
     * @return this is the string representation of the given value
     */
    public String write(Object value) throws Exception {
        int length = Array.getLength(value);

        if (entry == char.class) {
            char[] array = (char[]) value;
            return new String(array);
        }
        return write(value, length);
    }

    /**
     * This method is used to convert the provided value into an XML
     * usable format. This is used in the serialization process when
     * there is a need to convert a field value in to a string so
     * that that value can be written as a valid XML entity.
     *
     * @param value this is the value to be converted to a string
     * @return this is the string representation of the given value
     */
    private String write(Object value, int length) throws Exception {
        StringBuilder text = new StringBuilder(length);

        for (int i = 0; i < length; i++) {
            Object entry = Array.get(value, i);

            if (entry != null) {
                text.append(entry);
            }
        }
        return text.toString();
    }
}
